NANP area code
603
UTC−5, UTC−4 during daylight saving
- State
- New Hampshire
- Primary city
- Manchester
- Time zone
- Eastern
- In service
- 1947
NANP area code
603
UTC−5, UTC−4 during daylight saving
The code reaches 253 communities and 10 counties across New Hampshire.
The area code itself carries no risk signal. 603 is assigned to Manchester, New Hampshire, so a call from it is consistent with a real caller in that area — but the digits alone prove nothing, because they can be forged.
Caller ID is set by whoever places the call, not verified by the network. That is why neighbour spoofing works: an operation anywhere in the world can display a number that matches the area code — and often the first three digits after it — of the person being called, so the call looks local. Every community in the 603 territory is a plausible-looking origin for a forged 603 number, which is why one can be made to look like a neighbour to so many people.
If you did not recognise the call: let it go to voicemail — a legitimate caller with real business will leave one. Do not return the call using the number shown; look the organisation up independently and call the number you found. Never confirm personal details, card numbers, or one-time codes to someone who called you, however plausible the number looked.
Codes.zone publishes no complaint counts, risk scores, or caller identities. We hold no data on individual numbers and will not estimate what we cannot source.
Time there now
—
Eastern · UTC−5, UTC−4 during daylight saving
Reasonable callback window
8:00 AM – 9:00 PM
local time in Eastern
Federal rules bar telemarketing calls to a residence outside 8:00 AM–9:00 PM in the called party's own time zone. It is a sensible bound for a personal callback too — and a caller who rang you well outside it was not observing it.
603 is the only area code serving its territory — it has no overlay in the current numbering plan for New Hampshire. Where a region has no overlay, a number's area code still corresponds to a single geographic area.
| City | ZIP codes | County |
|---|---|---|
| Manchester | 8 | Hillsborough County |
| Nashua | 5 | Hillsborough County |
| Concord | 4 | Merrimack County |
| Portsmouth | 4 | Rockingham County |
| Rochester | 4 | Strafford County |
| Dover | 3 | Strafford County |
| Tilton | 3 | Belknap County |
| Hampton | 2 | Rockingham County |
| Keene | 2 | Cheshire County |
| Laconia | 2 | Belknap County |
| Lebanon | 2 | Grafton County |
| Acworth | 1 | Sullivan County |
| Alstead | 1 | Cheshire County |
| Alton | 1 | Belknap County |
| Alton Bay | 1 | Belknap County |
| Amherst | 1 | Hillsborough County |
| Andover | 1 | Merrimack County |
| Antrim | 1 | Hillsborough County |
| Ashland | 1 | Grafton County |
| Ashuelot | 1 | Cheshire County |
233 further communities not listed. All New Hampshire area codes →
Scope every community matched to 603. Source geoinfo-dataset (full_dataset) ZIP→NPA (2018 snapshot), GeoNames US postal codes (2026-07 postal dump) and Census 2024 county Gazetteer (2024 Gazetteer). Updated . Coordinates are place reference points, not boundaries.
We do not publish the NXX prefixes inside 603. The assignment of prefixes to rate centres comes from LERG routing data, which is proprietary, and we will not estimate it from postal data — ZIP codes and telephone prefixes do not map onto each other. Awaiting a clean-rights NPA-NXX source.